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A unique sensing system is described using an ultrasonic transducer for measuring tree trunk diameters in the orchard. Trunk diameters were calculated from the time it took sound waves to travel from the transducer to the trunk and back to the sensor. The device was calibrated with objects ranging in diameter from 1.6 (0.63 inch) to 19.0 cm (7.5 inches). The distance between the transducer and object was reduced as the diameter increased and was highly correlated (P = 0.99) with actual diameter. The ultrasonic tree diameter sensor exhibited a mean error of 0.04 cm.
An apparatus was designed to deliver low-dose UV-C light to the surface of fruit on a processing line and tested for its control of postharvest decay. It consisted of a row of UV-C emitting lamps mounted on a frame above a conveyer belt that transported the fruit. The dosage of the UV-C light delivered to the fruit surface was regulated by varying the speed of the conveyor belt. Postharvest decay after 28 days storage of `Empire' apples was reduced 52% relative to the untreated checks when the fruit were conveyed at 6.2 m·min−1 (1.38 kJ·m−2 dose) under the UV-C apparatus. Factors affecting the practical application of UV-C irradiation of fruit for controlling postharvest decay are discussed.